Excellent electromagnetic wave absorption properties of porous core-shell CoO/Co@C nanocomposites derived from a needle-shaped Co(OH)2@ZIF-67 template

Metal-organic-frameworks (MOFs) have attracted wide attention in the preparation of microwave absorbing materials because of their developed abundant porous structures. Compositing magnetic oxide into MOFs could significantly enhance the microwave absorption ability. In this work, a CoO/Co@C nanocomposite was prepared by calcining a needle-shaped Co(OH)(2)@ZIF-67 template at different pyrolysis temperatures (500-650 degrees C). Furthermore, CoO and Co particles were embedded into porous carbon frameworks, creating ample surfaces and interfaces. The core-shell and porous structure is beneficial to microwave absorption (MA). In addition, it is obvious that the calcination temperature has a significant impact on the microwave absorption properties of the samples. In detail, when the calcination temperature is 550 degrees C, the samples exhibit the best microwave absorption properties. A minimum reflection loss (RLmin) of -38.46 dB is obtained at 16.12 GHz with a coating thickness of 1.5 mm, and the maximum effective absorption bandwidth (RL <= -10 dB) can reach 4.8 GHz (9.68-14.48 GHz) at a coating thickness of 2 mm. Such excellent MA properties are attributed to the outstanding magnetoelectric synergistic effect and well-matched impedance. (C) 2020 Elsevier B.V. All rights reserved.